Patent GB-609482-A (GB)
Title: Manufacture of 2:5-dichlorostyrene and polymerization products thereform
IPC: C07C17/35
Filed: 1944-11-27
Abstract: Polymerization products are manufactured by polymerizing 2 : 5-dichlorostyrene alone or jointly with another polymerizable substance containing an ethylenic double bond, especially a vinyl or vinylidene compound such as aromatic vinyl compounds, vinyl esters, esters of unsaturated acids, aliphatic a  : b -unsaturated acids or anhydrides or unsaturated hydrocarbons or their halogen derivatives. The polymerization may be carried out at room temperature or at a raised temperature, preferably about 50-150 DEG  C., and may be accelerated by the action of ultra-violet light or by the addition of a polymerization catalyst, e.g. benzoyl or acetyl peroxide.  The products may be used for the manufacture of insulating articles, especially for high-frequency work, e.g. switch plates, coil formers, insulating beads, jacks, bushings, safety shields, panels, cable connectors, conduits, insulating cups, plugs, sockets, microphone connectors, or insulator tubes, or of other moulded articles, turnery articles or coatings.  In examples: (1) 2 : 5-dichlorostyrene is heated to 60 DEG  C. for 24 hours and then to 150 DEG  C. for a further 24 hours; (2) 2 : 5-dichlorostyrene is heated to 60 DEG  C. for 12 hours, then to 80 DEG  C. for 12 hours and finally to 150 DEG C. for 24 hours; (3) 2 : 5-dichlorostyrene is heated to 30 DEG  C. for 72 hours, then to 80 DEG  C. for 24 hours and finally to 150 DEG C. for 24 hours.  Specifications 510,450, 564,828, 564,829, 570,596, 588,605, 596,295 and 596,296 are referred to.ALSO:1 - Monochlorethyl - 2 : 5 - dichlorobenzenes are manufactured by chlorinating 1-ethyl-2 : 5-dichlorobenzene (itself obtainable by chlorination of ethylbenzene or by ethylation of p-dichlorobenzene with ethylene), preferably with exposure to ultra-violet light.  In an example, ethylene is passed under pressure into fused p - dichlorobenzene containing aluminium chloride (or other Friedel-Crafts catalyst, e.g. zinc chloride, titanium chloride or stannic chloride) and the resulting 1-ethyl-2 : 5-dichlorobenzene is treated with chlorine in the light, preferably in the presence of phosphorus trichloride or pentachloride, to produce a mixture of 1-(a - and b -chlorethyl)-2 : 5-dichlorobenzene (the former predominating), which may be separated by fractional distillation.  1 - Monohydroxyethyl - 2 : 5 - dichlorobenzenes are manufactured by hydrolysing the corresponding monochlorethyl compounds, e.g. by means of caustic alkali, preferably in solution in a mutual solvent for the reactants, such as a lower aliphatic alcohol.  In an example, 1-(a -or b -chloroethyl)-2 : 5-dichlorobenzene or a mixture thereof is refluxed with sodium or potassium hydroxide in methanol, ethanol or propanol.  2 : 5-Dichlorostyrene is manufactured by: (a) preparing a 1-monohydroxyethyl-2 : 5-dichlorobenzene as above and dehydrating it at a raised temperature in the presence of a dehydration catalyst; or (b) eliminating hydrogen chloride from a 1-monochlorethyl-2 : 5-dichlorobenzene by heating it, preferably in the presence of a contact catalyst (other than a catalyst comprising an intimate mixture of a phosphate of an alkaline earth metal with the phosphate of a metal of variable valency), e.g. by passing it with superheated steam over the catalyst, preferably at 400-500 DEG  C.; or by treating it with pyridine and decomposing the resulting complex; or (c) dehydrogenating 1-ethyl-2:5-dichlorobenzene at a raised temperature in the presence of a dehydrogenation catalyst.  In examples: (1) 1-(a - or b -hydroxyethyl)-2:5-dichlorobenzene or a mixture thereof is passed through a tube at 400 DEG  C. containing aluminium oxide (or other dehydration catalyst, e.g. activated carbon, graphite, thorium oxide, pumice or red phosphorus); (2) 1-(a - or b -chlorethyl)-2:5-dichlorobenzene or a mixture thereof is passed with superheated steam at about 450 DEG  C. over activated charcoal (or aluminium oxide); (3) ethylbenzene is chlorinated and the resulting 1-ethyl-2:5-dichlorobenzene is passed through molten lead in the presence of activated carbon.  Specifications 510,450, 564,828, 564,829, 570,596, 588,605, 596,295 and 596,296 are referred to.